Sustainable management of complex social-ecological systems depends on understanding the effects of different drivers of change, but disentangling these effects poses a challenge. We provide a framework for quantifying the relative contributions of different components of a social-ecological system to the system’s outcomes, using forest fires in the western United States as a model. Specifically, we examine the difference in wildfire probability in similar forests under different management regimes (federally managed vs. privately owned) in eleven western states from 1989–2016 and compare the magnitude of the management effect to the effect of climate variables. We find a greater probability of wildfires in federally managed forests than in privately owned forests, with a 127% increase in the absolute difference between the two management regimes over the 28 year time period. However, in 1989, federally managed forests were 2.67 times more likely to burn than privately owned forests, but in 2016, they were only 1.52 times more likely to burn. Finally, we find that the effect of the different management regimes is greater than the marginal (one-unit change) effect of most climate variables. Our results indicate that projections of future fire probability must account for both climate and management variables, while our methodology provides a framework for quantitatively comparing different drivers of change in complex social-ecological systems.